Currently, practical use of regenerative medicine, in which attempts are made to regenerate a body tissue or organ whose function is deteriorated or impaired, is being promoted. Regenerative medicine is a new medical technology in which a body tissue that cannot be recovered by the self-healing ability is reconstructed using three factors, that is, cells, scaffolds and growth factors, such that the tissue has a morphology and/or function similar to those of the original tissue.
In the field of regenerative medicine, collagen or gelatin, which has high biocompatibility, is used in some cases for the purpose of, for example, helping tissue repair or regeneration by cells. In particular, collagen or gelatin is sometimes used for regeneration of a tissue having a three-dimensional structure such as bone or skin, and, for the purpose of achieving better tissue regeneration, various modifications are being made for collagen and gelatin.
Cartilage, for example, articular cartilage, is a tissue composed of a very small amount (about 2%) of cartilage cells together with an extracellular matrix, and the extracellular matrix is known to contain about 70% water, about 20% collagen and about 10% proteoglycan. The proteoglycan in the extracellular matrix is a glycoprotein containing a polysaccharide called glycosaminoglycan (GAG) in an amount of about 95%, and about 5% protein. In a cartilage, cartilage cells are supported by being surrounded by collagen or proteoglycan produced by the cartilage cells themselves. In particular, glycosaminoglycan is thought to be a substance playing a role in keeping water in the cartilage matrix and involved in suppression of deterioration of, or in repair of, cartilage. Thus, studies are being carried out to develop a scaffold material for cartilage cells, which scaffold material allows favorable matrix production by the cartilage cells.
As a scaffold material for cartilage cells, natural form of type II collagen is conventionally used.
Japanese National-Phase Publication (JP-A) No. 2007-528699 discloses a cell support coated with an RGD-enriched gelatin-like protein with enhanced cell binding capacity, and describes that such a cell support can be used for skin grafting, wound healing, or enhancement of the growth (regeneration) of bone or cartilage.
WO 2008/133196 discloses a recombinant gelatin having an RGD sequence as a cell adhesion signal, and describes that such a gelatin can be used as a cell-adhesive matrix. WO 2008/133196 also describes that, in cases of cell therapy, a cell-adhesive matrix material that can be used as a scaffold for cells is generally preferred, and that, in cases of cartilage regeneration, a high-strength matrix is desirable.